KITCHEN HOOD CONTROL

20% of Energy costs are related to conditioned air

The average food service kitchen exchanges inside air for

fresh outside air at least 20 times per hour. It sounds

like an effective way to keep a kitchen comfortable and

safe, but in most situations it is actually a huge drain on

energy resources that provides no real health benefits

to employees or guests. Roughly 25% of a food service

operations energy costs go to conditioning the outside

air brought in during these air exchanges, and according

to estimates from the American Gas Association, the U.S.

food service industry wastes more than $2 billion each

year because of excessive ventilation.

Excessive Ventilation

Technology is typically the culprit. Until a few years ago,

most kitchen ventilation controls consisted of a manual on/

off switch and a magnetic relay or motor starter for each

fan. Exhaust and make up fans either operated at 100%

speed or not at all, and the whir of the exhaust fan was a

common sound in the average commercial kitchen – even

when cooking equipment was not in use. Manual two

speed systems that relied on cools to switch from low to

high speed and vice versa offered some energy savings but

were seldom used efficiently.

Variable volume control

The kitchen control system has changed all that.

With microprocessor based controls whose sensors

automatically regulate fan speed based on cooking load,

time of day and hood temperature while minimizing

energy usage. The system includes a temperature

sensor installed in the hood exhaust collar, IP sensors on

the ends of the hood that detect the presence of smoke or

cooking effluent and variable frequency drives (VFD) that

control the speed of the fans.

Variable volume hoods reduce running

costs and increase equipment life

If you’re not using a variable volume hood it is always at

maximum design volume when running. The Kitchen

control system detects both smoke and temperature rise,

increasing the volume when it is needed. Most kitchen

hoods require full exhaust performance for only a small

percentage of the day. Varying the speed of the fan as

the cooking loads change will save money by reducing

ventilation needs.

BENEFITS:

a. The exhaust volume for a kitchen hood can be significantly reduced.

b. The energy costs of the input air heating and cooling system may be

significantly reduced.

c. The carbon footprint will be reduced.

d. A quieter kitchen - Even relatively small decreases in speed can reduce

the kitchen noise level. When the fans run at 80 percent speed, the air

noise generated at the grease filters decreases more than 20 percent;

when the fans run at 50 percent speed, air noise is virtually eliminated.

The result: a more pleasant environment for employees and guests (when

the hoods are located near customers).

e. Reduced HVAC equipment wear - Soft-starting the hood fans with a VFD

extends belt life, reducing the make-up airflow decreases the rate at

which the filters become dirty and need to be cleaned or replaced.

f. Decreased grease entrapment - Excessive fan speeds send grease up the

duct, into the fan and out to the building roof and, sometimes, even into

the atmosphere. Slowing down the exhaust fans and reducing the air duct

velocity allows the grease to drain back to the hood and into grease cups,

where it can be easily disposed of, which reduces the frequency that the

hood and ducts need to be cleaned.

g. The system may be readily linked to a computerized building

management system.